Heart disease resulting from cardiac contractile dysfunction is the number one killer of people in the US today. The proteins that regulate cardiac contractile are under the tight post-translational modification (PTM) regulation of kinase phosphorylation and phosphatase de-phosphorylation. Central to the regulation of cardiac muscle contraction is the troponin (Tn) protein complex. In response to cardiac stress the Tn complex is subjected to a number of PTMs. Phosphorylation represents the primary mechanism of muscle PTM and it's tight balance is critical to normal heart function. Other non-phosphorylation Tn PTMs also occur. To date most Tn protein PTMs have been studied as isolated events, however the combined function of multiple Tn PTMs cannot be determined from function of the isolated events. This proposal investigates the primary troponin contractile regulation phosphorylation and other novel PTM events as combined events to better understand the physiological regulatory function of Tn PTMs as they occur in the heart. To this end, we will employ model troponin proteins and transgenic animal models containing single or multiple PTMs to evaluate biochemical and animal level function. The goal of these studies is to develop a more physiological understanding of the events that regulate heart function in order to identify novel drug targets to treat cardiac dysfunction.